Animation positions and animate along the path - Animation nodes
For the first question:

It seems you need the Object ID Key feature to store the initial transformation info for the objects. Here is how to use the Object ID Key node:



IMHO, the whole nodetree could be optimized like this:





For the second question:

A basic example setup would be:




BTW, there is a nice template called Distribute Instances on Spline, which is a great start to learn how to make things working like this. You can find it in Templates menu on Node Editor's header.